Nuclear power plants are periodically inspected for the sake of maintaining safety and reliability of the plant structures and various devices. In particular, reactor internal structures are often inspected by indirect visual inspection using an underwater TV (television) camera or a TV camera accommodated in a watertight case. Among conventional examples of such an in-core visual inspection apparatus using an underwater TV camera is disclosed in Patent Document 1.
The inspection method disclosed in Patent Document 1 is to immerse a remote-controllable TV camera into the reactor to shoot an inspection object, and the human inspector visually checks the picture of the TV camera which is output on a monitor. Simultaneously with the inspector's visual observation, the moving picture is recorded on video tapes, optical disks, or the like. If any defect is found in the inspection object, the inspector checks the recorded picture to create an inspection record on the defect.
PATENT DOCUMENT 1: Japanese Patent Application Laid-Open Publication No. 2000-346976
PATENT DOCUMENT 2: Japanese Patent Application Laid-Open Publication No. H 03-214978
PATENT DOCUMENT 3: Japanese Patent Application Laid-Open Publication No. H 04-154292